An application of uncertainty analysis to rock mass properties characterization at porphyry copper mines
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ORIGINAL PAPER
An application of uncertainty analysis to rock mass properties characterization at porphyry copper mines Masoud Mazraehli 1
&
Shokrollah Zare 1
Received: 1 October 2019 / Accepted: 17 February 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Deterministic methods have been widely used for estimation of rock mass properties. It is, however, accepted that there are some sources which impose uncertainties on rock mass properties. Spatial variability is one of the uncertainty sources that must be considered in design stage. In this study, a stochastic procedure is presented for characterization of rock mass properties at a porphyry copper mine in which the spatial variability is typically observed so that the uncertainty in rock mass properties plays a huge role in its quality. Intact rock data obtained during an enormous experimental campaign are statistically analyzed to ensure that they have been collected from a probabilistic society. Then, structural ratings of the rock masses and surface conditions of the structures have been mapped in the field. Finally, a particular stochastic code has been developed in matrix laboratory to evaluate the intrinsic uncertainty of obtained geomechanical properties at the depth of planned underground openings based on HoekBrown failure criterion. The results show that rock mass properties might not necessarily follow probability distribution functions of intact rock and joints properties. Moreover, gamma distribution function has been determined as the best fitted distribution function for rock mass uniaxial compressive strength. On the other hand, it was observed that rock mass tensile strength and its deformation modulus are lognormal variables. Keywords Probability . Stochastic analysis . Monte Carlo simulation . Spatial variability . Rock mass properties . Underground mining
Introduction Estimation of rock mass properties is one of the most important issues in the preliminary stages of a rock engineering project. Rock mass properties are considered as input parameters for design stage of the project, and incomplete investigations would impose some technical and economic problems such as unstable design or, on the other hand, high-cost support system requirements. For these reasons, it is crucial to have a complete perspective on the geomechanical properties of a project which is possible through employing a robust investigation technique.
* Masoud Mazraehli [email protected] Shokrollah Zare [email protected] 1
Faculty of Mining, Petroleum and Geophysics Engineering, Shahrood University of Technology, Shahrood, Iran
Direct and indirect methods are usually used to determine rock mass properties as conventional procedures. Direct technique includes laboratory and in situ tests. It is obvious that preparing a representative rock mass sample in lab-scale and also test apparatus is almost impractical. Moreover, in situ tests are expensive for the preliminary design stage of a project due to lack of financial resources.
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